According to the Insect Museum of West China, an expedition to the outskirts of Chengdu in mid-July returned dobsonflies with 8.3-inch wingspans and "giant snake-like fangs."

Entomologists say the presence of the giant dobsonfly, native to China and Vietnam, is an indication of clean water nearby.

Large enough to cover the face of a human adult, this scary-looking insect is also known among entomologists as an indicator of water quality, says the museum.

The giant dobsonfly makes its home in bodies of clean water and is highly sensitive to any changes in the water's pH as well as the presence of trace elements of pollutants. If the water is slightly contaminated, the giant dobsonfly will move on to seek cleaner waters. (CNN)